The present invention relates to radio communication apparatus connected to information processing apparatus such as a personal computer and a PDA, characterized by a compact design for carry-along applications and reduction in a high-frequency noise component entering the high-frequency circuit of the main unit, the noise component originating from the control circuit of information processing apparatus such as a personal computer or a PDA and coming into a receiving frequency of the main unit.
Conventionally, it was a customary practice to use a 1/4.lambda. to 3/8.lambda. whip antenna as an antenna for radio communication terminal apparatus where a high-frequency circuit, a communication control circuit, an antenna and a PCMCIA interface were integrated.
FIG. 4 shows a configuration of conventional radio communication terminal apparatus that uses a 1/4.lambda. whip antenna. The radio communication terminal apparatus is characterized in that a circuit board 131 is composed of a high-frequency circuit 130, a communication control circuit 132 and a PCMCIA interface 133 and that the antenna is integrated by connecting the high-frequency circuit 130 and the 1/4.lambda. whip antenna 126.
A 1/4.lambda. to 3/8.lambda. whip antenna requires a favorable ground for operation as an antenna. For radio communication terminal apparatus that requires a compact design generally uses the ground for the circuit board 131 also as an antenna ground.
However, the conventional 1/4.lambda. to 3/8.lambda. whip antenna requires a broad and stable ground surface in order to obtain stable characteristics. While the circuit board also plays the role of an antenna ground for radio communication terminal apparatus that requires a compact design, further downsizing is under way in recent radio communication terminal apparatus. This makes it difficult to provide a sufficiently stable and wide antenna ground.
For a one-piece design comprising a high-frequency circuit and a communication control circuit in radio communication terminal apparatus, there is a problem that, in case the role of an antenna ground was played by the ground for the communication control circuit, a high-frequency noise component enters the high-frequency circuit via the ground for the main unit, the noise component originating from the communication control circuit of the main unit and coming into a receiving frequency of the main unit.
Also in case radio communication terminal apparatus is connected to information processing apparatus such as a personal computer and a PDA, there is a problem that a high-frequency noise component enters the high-frequency circuit via the ground for the main unit, the noise component originating from the control circuit of the information processing apparatus and coming into a receiving frequency of the main unit.
Thus, incasea high-frequency component noise originating from the communication control circuit of radio communication terminal apparatus or from the control circuit of the information processing apparatus and coming into a receiving frequency of the main unit is a noise signal whose frequency is the same as the receiving frequency, there arises a problem of a cochannel suppression interference.